A pair of new Omicron subvariants has emerged, raising the possibility that survivors of earlier Omicron strains can get reinfected. BA.4 and BA.5 have gained increasing attention in South Africa as weekly coronavirus cases tripled in the last two weeks, according to data from Johns Hopkins University. “It really came out of the blue over the weekend. We were already settling down with BA.2.12.1, and then BA.4 and BA.5?” said Dr. Peter Chin-Hong, an infectious diseases expert at UC San Francisco. “It just seems like the latest chapter of a never-ending saga.” The rapid growth of BA.4 and BA.5 …